Antenna system for wireless communications



Feb. 11, 1930. I RQBINSQN 3,747,592?

ANTENNA SYSTEM FOR WIRELESS COMMUNICATIONS Filed March 19. 1923 3Sheets-Sheet l f are for EVZGJZ Z uZga lzwaiz M /7 an;

Feb. 11, 1930.

ANTENNA SYSTEM FOR wIRELEs COMMUNICATIONS Filed March 19, 1925 3Sheets-Sheet 2 E. Y. ROBINSON 1,747,027

Feb. 11, 1930. E. Y. ROBINSON E Y EZQZ? ANTENNA SYSTEM FOR WIRELESSCOMMUNICATIONS Filed March 19, 1923 5 Sheets-Shae; 3

y mfaw Patented Feb. 11, 1930 1,747n27 UNlTED STATES PATENT OFFEE ERNESTYEOMAN RGBINSON, GE WETHENGTON, ENGLAND ANTENNA SYSTEM WIRELESSCOMMUNICATIONS App1ication filed March 19, 19.3, Serial No. 626,139, andin Great Bri ain May 5, 1922.

This invention relates to antenna for wireof attaining these objects,will be best underless communication such as for wireless telegstoodwith reference to the accompanying raphy and telephony, and has for itsobject drawings in which Figs. 1 and 2 are diagrams to provide animproved construction of the representing the electrostatic field aroundan supporting structures or members of the anantenna, Fig. 3 is adiagrammatic representatenna, whereby the antenna may be insulated tionof a sectionalized mast in accordance in a more eiiective manner. Theimproved with the invention, Fig. l is a diagram illusconstruction alsoeliminates, or reduces, to trating voltage grading of a mast and Fig. 5a minimum the losses incurred by stray curis an electric diagram of theapproximate 10 rents which are normally induced in the supequivalentcircuits or the antenna. Fig. 6 porting members such as the masts, guys,and is a diagram illustrating a method of coupling the like. the mastsections. Fig. 7 shows one form of The invention comprises thecombination mast construction in accordance with the inof an antennasupported by one or more memvention, and Fig. 8 illustrates an antenna15 bers which are constructed in sections havsystem in accordance withthe invention. ing insulating breaks interposed between In Figs. 1 and 2the antenna is represented them and means for electrically grading tilein section by a circular disc placed parallel sections of the structureso formed, in order to earth, but it will be understood that the thatthe structure may be electrically graded invention is intended to beapplied to any 20 along its length. type or shape of aerial. In thefollowing The invention also comprises means for efdescription thesupporting members are retecting this grading by adjusting the variousterred to as masts and guys for convenience. electrical capacities ofthe sections of the sup- In Fig. l, which illustrates the electroportingstructure. static field around the antenna when no masts,

25 The invention further comprises means guys, or such like are present,the antenna is whereby the grading so produced by adjustrepresented bythe disc 1 which is connected ing the various electrical capacities ofthe to earth through the down lead 2. The elecsections may besupplemented by, or replaced tric field existing at any instant (saywhen by connecting the sections to suitable sources the antenna voltageis a maximum) is repreof electromotive force. sented in the conventionalmanner by equi- Vvireless antenna, as constructed at present, potentiallines 3. Fig. 2 illustrates the efusually consists of a wire network,supported feet of a conducting supportin member or above the earth bysuitable supporting memmast in proximity to the antenna. The mast bers,such as towers or masts, which may be is shown at l and theequipotential lines are self-supporting or guyed. The antenna isindicated at It will be seen that in the attached to the masts by meansof insulators, plane of the mast, the effect is to crowd the the saidinsulators taking up the whole of the major portion of the lines intothe space or voltage drop between the antenna and earth. gap 6 betweenthe antenna and the mast top,

According to this invention, a portion, or thus resulting-in said gap 6being subjected preferably the whole of the voltage drop may to a veryhigh electrical stress. This gap occur across insulators distributedalong the is very constricted and due to this fact and length of thesupporting structure. also to the fact that the insulators placed F orconvenience, the present invention will therein operate in extremelyexposed posibe described with reference to antennae which tion, it isdiilicult to design insulators which are supported by guyed masts, butit will be are able to withstand the high potentials on understood thatthe invention is equally and the antenna, especially at the highfrequency similarly applicable to all types of antenna at which thesepotentials are produced.

supports and their components, such for in- Moreover, as hereinbet'oreexplained, when stance as guys. the mast is constructed of electricallycon- The objects of this invention, and the means ducting material,currents which are sub- Lei antenna top eliminated.

stantially 180 degrees out of phase with the antenna current are inducedin the mast, which mast currents decrease the efliciency of the antenna.

According to this invention, the mast is constructed in sections, thesaid sections being insulated from each other. The sections areelectrically charged to definite potentials which potentials arealternating and substantially in phase with the potential on theantenna. The term potential as hereinafter used in connection with themast structure, or the like, will mean that the potential isalternating, and in phase with that potential'to which it is referred.It is arranged that the mastsections shall beat increasing potential asthe antenna top is approached, so that the mast as a whole, iselectrically graded along its length. By this means, the voltage at the.top of the, mast may be between the voltage of the antenna top andearth, or preferably it may be at the voltage of the antenna itself.WVhen the latter condition obtains, the antenna may be in directconnection with the mast top, and the insulation between the mast andThe arrangement affords a simple and effective method of insulating theantenna; moreover, the mast currents are prevented and hence the mastloss is eliminated.

hen the mast is so constructed, and is graded along its lcn t it may beplaced in proximity to the antenna without effecting the distribution ofelectrostatic field round the antenna (except in the immediateneighbourhood of the sections) if it is arranged that the sections areelectrically charged to the mean potential which the space they occupywould assume if the said sections were not present. Similarly, theinsulating breaks, since they prevent mast currents from flowing, willprevent the masts from affecting the distribution of magnetic fieldround the antenna. WVhen the mast is so constructed, insulation of theantenna may bev effected entirely by means of the graded sections of themast, the insulating breaks between these sections being suitablydesigned to withstandthe voltages to which they are subjected. Thetopmost section of the mast is preferably in electrical connection withthe antenna; it is preferably arranged that the antenna top embraces themast tops.

In Fig. 3 in which one mast is shown, the mast is constructed ofsections 7 which are insulated from each other by means of insulatingbreaks 8. The antenna is shown connected to the mast by means of theinsulators 9 but these may be omitted as has been hereinbefore stated.The sections '7 may be charged electrically to suitable potentials inorder to provide the required grading of the mast. In Fig. 4 two typesof grading are shown. The curve 10 shows the type of grading which maybe employed so that radiation from the antenna shall not be affected. Inthis case, the sections are charged to the mean potential which wouldexist in the space that they occupy. The curve 11 shows a uniformgrading of the mast which is preferable when the mast is to be insulatedfor extremely high Voltages in order that the voltage stress across themast insulators may be similar and equal, that is to say, in order thatthe insulators may be equally stressed.

According to one method grading of the mast structure isproduced byvarying the electrical capacity of the structure sections to earth, tothe antenna, and to each other; by suitably varying these capacities. ofthe sections (hereinafter these individual capacities will be referredto as component capacities) any desired grading may be produced. Forinstance, a grading corresponding to curve 10 (Fig. 4:) or a gradingcorresponding to curve 11 may be produced by suitably proportioning thecomponent capacities. In Fig. 5 the component capacities are represented by the letter C with prefix and sufix numerals; those across theinsulating breaks are denoted by the prefix 1, those between thesections and the antenna by the prefix 2 and those between the sectionsand earth, by the prefix 3. The suffix numerals denote the severalsections of the mast and the corresponding component capacities.Capacity 6 re-' not adjacent; it would also be necessary tov considerthe standing wave on the antenna. However, for the purpose of thisdescription,

it is sufficient to consider only the capacities referred to above. Byvarying these component capacities, the grading of the mast may bealtered as desired.

The component capacities may be given the desired values by suitablyproportioning.

the mast sections. The most important dimensions in this respect, arethose of the sec- 7 tion ends. The mast may also be graded by means ofcondensers connected from the sections to the antenna, to earth, andalso connected between adjacent sections. In the preferred method, whencondensers are em ployed, the adjacent section ends are connected toeach other by means of condensers. These may consist of metal discs orthe like situated on each side of the insulating break,

or the condenser may be a separate unit con- 7 nected electrically, andpreferablv mechanically, to the section ends. In the latter case,

the condensers are preferably of the air dito a source of electromotiveforce in resonance with and preferably substantially in phase with thevoltage on the antenna. This electromotive force for supplying thesections may be suitably derived from the source supplying the power tothe antenna. The sections may be energized for example by connectingthem to the secondary of atransformer whose primary is coupled to thepower source. In the preferfed method it is arranged that the sectionsare connected to tappings on an oscillation transformer which may becoupled to the antenna loading coil, or may be excited in any desiredway. WVhen the antenna is excited by means of a high frequencyalternator, the sections may be connected to tappings on the alternatorwindings.

Referring to Fig. 6, power is supplied along leads 13 and the antenna iscoupled thereto by means of a transformer formed by the windings 14 and15. The exciting current passes through a winding 16 which is coupled toan oscillation transformer formed by an inductance 17 and capacity 19.The mast sections 7 are connected to tappings 20 on the transformer 1617as shown. WVhen this arrangement is employed it is preferably arrangedthat the grading produced by the component capacities of the sections isequal and similar to the grading produced by means of the tappings ofthe oscillation transformer (if this is employed) in order that theoscillation transformer will not have to supply an appreciable capacityor charging current to the said sections.

Inasmuch as it may not be possible to accurately grade the sections whenthese are graded by adjusting the component capacities the mostconvenient method will be to grade the sections as accurately aspossible by adjusting the component capacities and finally adjusting thegrading by means of the tappings to the transformer, in which case thecharging current supplied by the transformer will only be that which isnecessary to compensate for the inaccurate capacity grading of thesections.

When the mast is guyed, the sections thereof may preferably bepin-jointed in order that no shear stress shall be placed on the sectioninsulators.

Referring to Fig. 7, the top of one section of amast is shown at 21 andthe bottom of the adjacent section thereof is shown at 22.

Such sections are insulated from one another by means of the insulator23 which preferably consists of porcelain, bakelit-e or the like. It isprovided with a large rain shed 24- whioh may preferably be provided onits underside with corrugations or petticoats 25 in order to increasethe length of the leakage path. Two metal supports 26 and 27 are fixedto the insulator 23 by means of suitable material such as, for instance,lead, or a lead alloy, so as to distribute the pressure on the surfaceof the insulator. The insulator faces and the corresponding supports 26and 27 may be suitably corrugated as shown at 28 so as to key orinterlock into each other. The metal support :27 is bolted or otherwisefixed to the top of the mast section 21. The support 26 has incorporatedin it, or attached to it, a curved metal surface 29 on which the mastsection 22 rests, the arrangement being such as to provide a limitedamount of relative movement between adjacent sections. Movement in alateral direction may be prevented by means for example of a pin 30 onthe curve surface 29 engaging in a corresponding recess 31 formed in thebase of the mast section 22.

The guys must be insulated in a similar manner because the mast sectionsoperate at high potentials. They are preferably insulated by means oflink type insulators, such, for example as Hewlett insulators. They aredistributed along the length of the guy and grading may be effected inthe manner hereinbefore described.

The insulators between the mast sections (and also between the guysections), may be provided with flash-over devices, such for example, asarcing horns in order to prevent a flash-over taking place on thesurface of the insulator. lVhen the condensers are connected across thesection ends, the flash-over device may preferably be incorporated inthe said condensers.

In the antenna system shown in Fig. 8 the antenna is supported by threesectionalized masts 4: which are constructed as hereinbefore described.Any desired number of masts may be employed. The masts are supported byguys such as 32 which are constructed in sections having the insulatingbreaks therebetween, the whole being graded as hereinbefore described. For clearness of illustration only the guys attached to one mast areshown. The antenna consists of three box shaped networks 83 which aresuspended as shown between the mast tops and are in electricalconnection with the latter. The downlead is formed by the net work 34.-as shown, connection to the antenna being preferably made at themid-points of the networks 33.

While the invention has been more particularly described with referenceto antenna for wireless telegraphy and the like, it will be understoodthat it is not limited thereto but may be employed for antenna for otherwireless purposes, such as wireless transmis sion of power.

It will be understood that various modifications may be made withoutdeparting from the scope of the invention.

I claim as my invention 1. A wireless antenna system embodyingsupporting members comprising sections which are insulated from oneanother and have component capacities, and means for exciting them fromsources of electro-motive forcein synchronism With the antenna current,said component capacities and excitation being proportioned to jointlygrade said sections electrically.

2.-A wireless antenna system as claimed in claim 1, wherein theexcitation grading is substantially equal to the capacity gradmg.

3. A wireless antenna system as claimed in claim 1, wherein the sectionsare excited by connection thereof with devices which are energized fromandin synchronism with the source of antenna excitation.

In testimony whereof I have hereunto subscribed my name this 5th day ofMarch, 1923.

ERNEST YEOMAN ROBINSON.

